How to Read Your Car Tyre's Sidewall Markings

The code on your tyre means something

Every car tyre carries a series of letters and numbers moulded into its sidewall. Once you know how to read them, you can check whether a replacement tyre matches your car’s specification, verify how old a tyre is, and spot a mismatch before it becomes a safety risk.

Tyre size: the 205/55 R16 example

Take the common marking 205/55 R16. Each part is a measurement:

205 is the section width in millimetres, measured across the widest part of the tread.
55 is the aspect ratio — the sidewall height as a percentage of the width. A 55-series tyre’s sidewall is 55% of 205 mm.
R stands for radial construction, the standard on almost all modern cars.
16 is the wheel rim diameter in inches, so this tyre fits a 16-inch wheel.

When you replace a tyre, keep the size identical to what the car maker specifies — usually printed on a sticker in the driver’s door jamb.

Load index and speed rating

After the size you’ll often see a code like 91V. The number is the load index: 91 means the tyre can carry up to 615 kg. The letter is the speed rating: V allows up to 240 km/h, while common ratings like H (210 km/h), S (180 km/h), and T (190 km/h) cover most daily cars. Never fit a tyre with a lower speed rating than the manufacturer recommends.

Finding the tyre’s age

Tyres harden and lose grip with age, even with plenty of tread left. Look for the DOT code, which ends with four digits in an oval — for example, 2524 means the tyre was made in the 25th week of 2024. Most experts recommend replacing tyres that are six years old or more, regardless of remaining tread.

A quick checklist before you buy

Match the full size code and load index to your car’s specification.
Confirm the speed rating meets or exceeds the factory recommendation.
Check the DOT date and avoid old-stock tyres.
Buy a full set of four when possible for balanced handling.

Reading the sidewall takes a minute, but it can save you from fitting the wrong tyre — or driving on rubber that is quietly past its safe life.